In conventional semiconductor-sized wafer processing methods, the wafer to be processed is commonly attached to an annular frame via a tape. The attachment of the wafer to the annular frame facilitates handling of the wafer in subsequent processing steps, such as grinding, cutting, dicing, e.g., blade dicing or laser dicing, or polishing.
A wafer, such as a semiconductor wafer, may have a plurality of devices, such as ICs (Integrated Circuits), LSIs (“Large Scale Integration”) or MEMS (Micro Electro Mechanical Systems), formed on the front side thereof. These devices are arranged on the front side of the wafer in separate regions which are partitioned by a plurality of crossing or intersecting division lines (also called “streets”). The wafer is divided along these division lines, in order to obtain a plurality of individual device chips.
In order to protect the devices formed on the wafer, e.g., from contamination by debris or cutting water, a protective tape or sheeting may be applied to the front side of the wafer prior to the cutting or dicing process. However, in particular, for the case of sensitive devices, such as MEMS, there is a problem in that the device structure on the wafer may be damaged by the adhesive force of an adhesive layer formed on the protective tape or sheeting or may be contaminated by adhesive residues on the devices, when the tape or sheeting is peeled off from the wafer.
In order to overcome the above-identified problem, a wafer processing method has been proposed in U.S. Pat. No. 8,815,644 B2 in which a ring adhesive tape having an annular adhesive layer only in a peripheral area thereof is attached to the front side of the wafer. The annular adhesive layer of the ring adhesive tape is positioned so as to correspond to a peripheral marginal area of the wafer in which no devices are formed. In this way, any damage or contamination of devices formed in a device area of the wafer due to the adhesive layer can be prevented.
According to the wafer processing method disclosed in U.S. Pat. No. 8,815,644 B2, the wafer having the ring adhesive tape attached thereto is subjected to a back side grinding step, while holding the wafer on a chuck table. Subsequently, the ring adhesive tape attached to the front side of the wafer is attached to a support tape which is held by an annular frame. By means of the support tape, the wafer is held on another chuck table and modified layers are formed inside the wafer by applying a suitable laser beam from the back side thereof.
The wafer processing method discussed above thus requires the use of at least two different tapes, namely the ring adhesive tape and the support tape. In a first step, the ring adhesive tape has to be aligned with the wafer to be processed and, in a second step, the wafer with the ring adhesive tape attached thereto has to be aligned with the support tape.
Hence, there remains a need for a protective sheeting or tape for use in semiconductor-sized wafer processing which allows for the processing operation to be simplified, reducing both the number of processing equipment components required and the number of processing steps.